1. Field of the Invention
This invention relates to a fluidic control assembly for controlling the delivery of air and/or water to dental equipment and, more particularly, to a fluidic control assembly for a dental tool such as a handpiece.
2. Description of the Prior Art
Conventional dental drills are operated at relatively high speeds by an air turbine driven from a source of air at a regulated pressure. High speed dental drills usually also have provision for discharging water as a stream, or jet in direct proximity to the drill. Likewise air may be delivered either with or without the drill itself being turned on. Water and air are supplied to the drill from separate water and air supply source in the dental office.
It is typical for the supply of air and/or water to be operated from a foot switch under the control of the dentist. In addition to the foot switch, a control assembly is used to automatically control the supply of drive air to the dental drill and to discharge a stream of water into the oral cavity. The control assembly is generally designed to operate in response to the removal of the tool or handpiece from its cradle. Prior art control assemblies are designed to use pneumatic valves in combination With electrical and/or hydraulic controls to form a complex and expensive control unit, which is difficult to install and generally requires a substantial amount of expertise to repair and maintain.
A more recent control arrangement developed by applicant uses a modular fluidic block design as shown and described in U.S. Pat. No. 4,459,106. Although the fluidic block forms a compact control unit, it is operationally dependent upon the accuracy in alignment between a source of compressed air and a sensing chamber for detecting the presence or absence of the handpiece in its hanger. A laminar flow of air must bridge an air gap and strike a diaphragm in the sensing chamber When the tool is removed from the hanger. The tool otherwise fills the air gap, blocking the air flow. Accordingly, the accuracy in alignment between the source of compressed air and the sensing chamber is critical to the operation of the control unit and requires each unit to be factory tailored and tested. Moreover, the operation between the control unit, the handpiece, and the valve diaphragm in the sensing chamber are so mechanically interrelated that specialized personnel are necessary to undertake the installation of the control unit in the dental office. In addition, the control unit is part of the hanger assembly and cannot be separated for repair. Accordingly all repair must be done directly in the dental office or the entire assembly, including the handpiece and hanger, must be removed from the dental office.
A substantial need has developed for a more simplified control unit, and preferably of miniature size which requires no special training to install, is easy to maintain, and may be physically independent of the hanger assembly so that the control unit can be repaired simply by replacement with a substitute unit While the inoperative unit is returned to the factory.